Rubber product and method of making same



Patented Oct. 9, 1934 j um serene -13 s 1%r: Es PIA'TTEN r @F-FEQET RUBBERPRODUOT AND METHOD OF MAKING SAME John Helfrich,

No Drawing; Application July 30, 1931,

Serial'No. 554,165

12' Claims;

This invention relates; generally; to rubber;

and r the invention relates, more particularly, to

a new andimproved-rubber product,anda newand improved method of maki'ng the same.-

One of the ob'jects of my invention is-to produce a rubber product -from--1atex, which-shall be sufficiently non-tacky, shall maintain its elasticity and fiexibility, and can: be treated with a great many binding and-fillingmaterialsiwith Liv lit outthe common necessity of Vulc'anizingthe rub-'- product is a compound 'of rubbe'r and a suitable aluminu-mchromium or ironsalt. L V 1 Another object "of invention is -to provide a 25curedfrom latex '-or any other suitable rubberdispersionwwhich paste can =be= used= forz impregnatingfabrics or fdr variol1sothr purposes; 1 and which displaysthe desired properties :of resistnum,-chromium or iron, that a smooth spreadable paste is secured from the latex, and that 'for example, is treated with a basic salt of alumithis paste has many desirable properties which will be later set forth.

Byway of example, the invention may bedescribed by using basic chromium salts. Amongst the chromiumsalts which I have found satisfacis in its trivalent form. For example, basic chrotory are basic chromium salts wherein chromium" mium sulphate (Cr. (DY-1.804) or basic chromium-- chloride (Crz (OI-D3 C13) may be used. Prefer ably a neutral salt or salts such as sodium sulphate, sodium chloride or sodium acetate is added i along with the basic chromium salt to the rubber dispersion. These neutral salts evidently serve as buffers oragents for lowering the hydrogen I ion==concentration resulting fromthe hydrolysis of the-basic-chromium compound used. After the basic salt and the latex have beenallowed- 7553 to react fora suflicient period-I prefer to neutraliz'e any acid which may be present in the reaction mass due to the hydrolysis of the basic m th d-wh r yapr adabl pa t an b -s salt,'by-adding'a sufficient amount of analkali such assodium bicarbonate or borax.

While-{do not wish to limit myself to the'speonic-operations and proportions, or-to the-se quenceof steps specified in-the preferred exama e temperature h n v sufiicient freedom ple of my invention; practical working directions" 3U from"tackiness; -flexibfli ty-and extensibility; without requiring a subsequent vulcanization operation.--

Other objects of-my '-invention=willbe set forth inthefollowing sdescription which illustrates :a 3i preferred "embodiment l thereofiitbeing sJ-understoo'd ithat the-above generalstatement lot the:

' are'=as follows;-

'A-5 %-'solution-of basic chromic sulphate is pre- SO EFT pared by -disfsolving grams of the salt in 100" cc:-of distilled water. Thebasic chromic sulphate is preferably the commercialsalt which'is anhydrous and which normally contains approximately 'to percentby weight of sodium sul- Objects of y nvention is intendedto ge a yphate', which neutral salt content evidently fifirevent 'a stable arubberr'produciplwhich wouldibe-r ordinarily containsabout 36 parts of latex sol-ids sufficiently noneta'ckysand :resistant; to: temperature-changea -could notzbe securedrsave by vulz-x It' ha's heretofore been well known to .coaguserves asa buffer as previously mentioned. 100

ccu'of Water are then added to the solution thus -giving a total=vo1u1ne of 200 cc. To this 200 cc;

.i of the-basicchromium salt solution, I now add ii 100 cor-of ordinary latex which has been pre-' served with a small quantity of ammonia or other alkali in the ordinary commercial way, andwhich by VOllllllel The latex is gradually added to the 1 basic: chromium salt solution :with constant canization byimeanszof sulphursxThe vulcanizax-l mixingv: The reaction between thebasic chromition. stepunwasuexpensivemtand :objecti'o'nable:"for um compound or salt and the latex isexceedingly various; reasonxzespeciallysini vulcanizingn:rub--- rapid and-is complete within a few minutes.-

ber 'tiresrior :othervarticles .made-wwholly-i-or. in

part; of rubber, whererdongstreatment: and high temperature were necessary.

I have discoveredethatiwhen an :ordinary .latex -preserved in zthe-"ordinary wayi aswith ammonia;

E; Preferably the mixture is allowed to stand for ,1 onez-half-hour before'further treatment, although 1 the mixture may be allowed to stand for a much-i. longer'ntime: or even indefinitely withoutxin jury y thereto; :if desired.

25. ordinary use.

65 contained 155.2 grams of total solids.

orcusly mixed with the reaction mass.

The reaction mass is then filtered by any suitable method such as by suction for example, and a smooth spreadable paste is separated from the liquid constituents of the reaction mass. This paste may be pressed between two pieces of cloth,

such for example, as ordinary duck, to more thoroughly dry it and to shape it to any desired form, and the cake thus produced is then dried by exposing it to ordinary room temperature or by gently warming it as by allowing dry air to circulate over it or by heating in an oven or the like to a temperature of approximately 220 F.

The resultant product is strong, extensible and flexible, and it also is sufficiently non-tacky for It is much more extensible than ordinary vulcanized rubber. It does not lose these desirable properties upon being heated to a temperature high as 220 F. Upon examination with the ultramicroscope, it can be seen 01 that the chromium salt is very uniformly and intimately combined with the latex. A true compound has been formed with the latex, producing a desirable rubber product of uniform texture. Evidently the chromium basic salt ions in com- 5.' bining with the latex particles constitute a stabilizing or protective agency which permits the rubber to retain its well-known desirable properties, while enhancing some of said desirable properties. Likewise, an examination with the ultra- 4 microscope shows that the rubber particles have not aggregated, but that they have substantially the same size as in the original latex or rubber dispersion.

Likewise, the final product cannot be rendered ,too tacky and it cannot be swelled by being immersed in water. The smooth paste can be used for impregnating any suitable fabric in the ordinary manner, and when the paste has dried and set, it renders the fabric perfectly waterproof.

;;By removing all of the moisture from the product, the same can be reduced to powdered form as, for example, by spray drying, and molded to any desired shape, either by itself or in conjunction with other materials, such as zinc oxide or ,;any other suitable fillers.

Upon analyzing a sample prepared as above mentioned, save that 450 cc. of the basic chromium sulphate solution (analyzing at about 2/2% of chromic oxide (CI2O3) were utilized, to-

60, gether with 450 cc. of distilled water and 450 cc.

of latex, (including treatment with sodium bicarbonate) the following was determined:-

The chromium solution contained 1134 grams of available chromic oxide (ClzOs). The latex Upon ashing a sample of the dried and set material whose weight was .685 grams, I found that the weight of the ash was .047 grams. In preparing the paste above mentioned, the filtrate is colorless and upon testing this with sodium peroxide in the ordinary manner, the familiar yellow color is not produced, so that it seems clear that the filtrate is free from chromium or any salt thereof, showing that the chromium salt has combined .with the rubber in the latex. This is confirmed by the abnormally high percentage of the ash, found as above mentioned. The ash secured by the above test had a distinctive green color which would indicate the presence of chromic oxide. Upon fusing the ash thus produced with a potassium carbonate-sodium carbonate fusing mixture, I determined that the percentage of chromium oxide in the ash was 98.76%.

I have also found that before the paste secured as above mentioned has dried and set, that it may be mixed with various fillers such as clay, zinc oxide, carbon black and other well known filling and coloring materials commonly used for filling and coloring rubber. By adding sufiicient filling material to the rubber such as, for example, by preparing a mixture containing of the paste, 10% of clay, and 10% of zinc oxide which are thoroughly intermixed before the mixture is allowed to dry and set, a stiff, strong and resilient block of material can be made which resists great bending pressure. Hence, it is to be understood that when I claim the novel composition, it is intended to include a composition of pure rubber, or of rubber intermixed with a filler.

While I do not wish to limit myself to any definite theory of operation, I believe that the following occurs.

When an ordinary coagulant salt is added to latex, such as calcium chloride for example, the coagulant merely reacts with the proteins or other non-rubber colloids in latex. If there is any reaction, either physical or chemical, between the rubber and the salt, this does not produce any appreciable effect because the coagulation is too rapid. By utilizing a basic chromium salt, a very slight acidity is imparted to the latex by the hydrolysis of the basic salt. This acidity is so slight that it cannot be detected by ordinary methods. It would require a hydrogen ion determination to detect the acidity of the latex mixture. This very slight acidity causes the rubber to coagulate very slowly so that the chromium or the chromium compound can combine with the rubber to form a true compound and to alter the properties of the rubber so-that it exhibits all the desirable properties of ordinary vulcanized rubber, as well as additional desirable properties, without the necessity of vulcanization. My invention is broadly new in that it produces a product comparable to ordinary vulcanized rubber without the use of sulphur and without any heating process, save the heat which may be employed for drying the paste more or less rapidly.

Likewise, while centrifugal separation is not necessary, it may be employed with advantage if it is desired to more quickly separate the paste from the latex.

As the result of careful experimentation, it has been found that the basic salts of two other trivalent metals, viz. aluminum and iron may be used in lieu of the basic chromium salts to form the novel rubber product of the present invention. For example, basic aluminum sulphate, or basic ferric sulphate may be substituted for the basic chromium sulphate given in the preceding example, and the resultant rubber product produced will have substantially the same desirable properties and qualities as the product produced by the use of the basic chromium salts. Therefore, it is not intended to limit this invention to the use of chromium salts alone, but it is intended to also include the use of basic salts or aluminum and of trivalent iron.

While I have shown a preferred method of securing the improved product specified herein,

the said product is broadly new and I do not wish that the claims therefore should be restricted to the specific method of manufacture disclosed herein.

Likewise, while I prefer to have the chromium, aluminum, or iron compound react with a rubber dispersion either natural or artificial, I do not Wish my invention to be restricted to the treatment of a rubber dispersion.

I have shown a preferred embodiment of my invention, but it is clear that numerous changes and omissions could be made without departing from its spirit.

What is claimed is:

1. The method of preparing a spreadable and stable paste from a rubber dispersion or latex, which consists in intermixing a basic salt of one of the three trivalent metals described with the rubber dispersion.

2. The method of preparing a spreadable and stable paste from a rubber dispersion, which consists in intermixing a basic salt of chromium with the rubber dispersion.

3. The method of preparing a stable rubber product from a rubber dispersion, which consists in thoroughly intermixing a mixture of a basic salt of chromium and a neutral salt, with the rubber dispersion.

4. The method of treating a rubber dispersion to produce a stable rubber product, which consists in causing rubber particles in the aqueous portion of the dispersion to unite with the ions of a basic salt of chromium in solution in the dispersion.

5. The method of preparing a stable rubber product from a rubber dispersion, which consists in thoroughly intermixing an aqueous solution of a basic chromium salt with the rubber dispersion and thereafter neutralizing any free acid which may have been formed during the reaction by adding a small quantity of an alkali.

6. A method of preparing a stable rubber product from a rubber dispersion, which consists in thoroughly intermixing an aqueous solution of a basic chromium salt and a neutral salt with the rubber dispersion, and thereafter neutralizing any free acid which may have been formed during the reaction by adding a small quantity of an alkali.

'7. As a new product of manufacture, a solid mass which is substantially stable when subjected to ordinary temperature changes, said mass containing rubber combined with a protective agent adapted to stabilize the same, said protective agent consisting of a basic salt of one of the trivalent metals chromium, aluminum and Iron.

8. As a new product of manufacture, a stable rubber product containing paste comprising a combination of rubber particles and ions of basic chromium sulphate.

9. As a new product of manufacture, a stable rubber product comprising a combination of rubber and the ions of basic aluminum sulphate.

10. As a new product of manufacture, a stable rubber product comprising a combination of rubber and the ions of basic ferric sulphate.

11. The method of preparing a stable rubber product from a rubber dispersion which consists in thoroughly intermixing a mixture of a neutral salt and a basic salt of one of the group of trivalent metals chromium, aluminum and iron with the rubber dispersion.

12. The method of preparing a stable rubber product from a rubber dispersion which consists in thoroughly intermixing an aqueous solution of a mixture comprising a basic salt of one of the trivalent metals chromium, aluminum or iron and a neutral salt with the rubber dispersion, and thereafter neutralizing any free acid which may have been formed during the reaction by adding a small quantity of an alkali.

JOHN HELFRICH. 

